The invention belongs to the technical fields of macromolecular synthesis and emulsions, and discloses a star-polymer stable pH responsive emulsion, a preparation method of the emulsion and application of the emulsion. The preparation method comprises the following steps that a star polymer is taken as an emulsifier, and an aqueous phase and an oil phase are stabilized, so that an oil-in-water emulsion is formed; the star polymer is CMSQ-PDMAEMA, and the structural formula of the star polymer is shown in the description. The emulsion disclosed by the invention has the advantages that an emulsion with a pH responsiveness is prepared by means of replacing a traditional emulsifier with the star polymer, the emulsion is demulsified when pH is more than 13, and the demulsified emulsion is restored into the uniform and stable emulsion when pH is in a range of 7 to 9; because of good thermal property and mechanical property which are specifically possessed by a polymer structure, the thermal resistance and tensile property of the emulsion are effectively improved; because of specific thermosensitivity, a polymer chain can be extended and retracted when a temperature is changed, so that the prepared emulsion can be applied to a plurality of fields, such as drug release on the basis of stimuli-responsive polymers, hydrogel and the like.